A radioiodinated vasopressin antagonist, d(CH2)5[Tyr(NH2)9]AVP has been prepared. Iodination was carried out at the phenyl moiety of the tyrosylamide residue at position 9, followed by HPLC purification. Non-radiolabelled monoiodinated antagonist was used as a reference for identification. 125I-d(CH2)5[Tyr(Me)2, Tyr(NH2)9]AVP binding appeared to take place with a dissociation constant of 0.28 +/- 0.09 nM (Kd +/- SD) to V1vasopressinreceptors on rat livermembranes.

radioiodinated

DEFINITION:

binding

DEFINITION:

dissociation constant

DEFINITION:

An equilibrium constant, expressed in concentrations, describing the dissociation of a molecule or ion into its components. Symbol Kd. See also acid dissociation constant and base dissociation constant . Called also ionization constant .

SD

DEFINITION:

Abbreviation for skin dose; standard deviation.

V1

DEFINITION:

Vasopressin-1.

vasopressin

DEFINITION:

1. One of two octapeptide hormones formed by the neuronal cells of the hypothalamic nuclei and stored in the posterior lobe of the pituitary gland (neurohypophysis), the other being oxytocin. It stimulates the contraction of the muscular tissue of the capillaries and arterioles, raising the blood pressure. It promotes contraction of the intestinal musculature and increases peristalsis, and also exerts some contractile influence on the uterus. It also has a specific effect on the epithelial cells of the distal portion of the uriniferous tubule, augmenting resorption of water independently of solutes, resulting in concentration of urine and dilution of blood serum. Its rate of secretion is regulated chiefly by the osmolarity of the plasma.

2. [USP], A pharmaceutical preparation of the same principle, prepared synthetically or obtained from the posterior pituitary of healthy domestic animals used for food by man; used mainly as an antidiuretic in the treatment of acute or chronic diabetes insipidus, administered intramuscularly as a test of hypothalamo-neurohypophysial-renal function in distinguishing central from nephrogenic diabetes insipidus; it may also be used to stimulate smooth muscle tissue, especially to induce vasoconstriction in the presence of hemorrhage. Called also antidiuretic hormone (ADH).

receptors

DEFINITION:

See definitions under "receptor."

liver

DEFINITION:

1. A large gland of a dark-red color situated in the upper part of the abdomen on the right side. Its manifold functions include the storage and filtration of blood, the secretion of bile, the excretion of bilirubin and other substances formed elsewhere in the body, and numerous metabolic functions, including the conversion of sugars into glycogen, which it stores.

2. The same gland of certain animals sometimes used as food or from which pharmaceutical products are prepared.